Question: What is the greatest common factor of $45$ and $30$ ? Another way to say this is: $\operatorname{gcf}(45, 30) = {?}$
Solution: The greatest common factor is the largest number that is a factor of both $45$ and $30$ The factors of $45$ are $1$ $3$ $5$ $9$ $15$ , and $45$ The factors of $30$ are $1$ $2$ $3$ $5$ $6$ $10$ $15$ , and $30$ Thus, the greatest common factor of $45$ and $30$ is $15$. $\operatorname{gcf}(45, 30) = 15$